Acoustic and physiologic methods are used to study speech development in children aged three to eleven years. The major objective of the acoustic studies is to describe and document a set of acoustic measures and features that can be used to determine how maturation affects the following properties of speech: (1) durations of selected phonetic segments and syllables, (2) temporal relationships within syllables and phrases, (3) short-term spectra associated with various vowel and consonant segments, (4) waveforms and long-term spectra of the laryngeal source for voiced sounds, and (5) selected spectrographic features useful in describing speech articulation. The primary methods of analysis are spectrograms and various digital techniques. The physiologic studies will provide descriptions of the motoric developments in the speech subsystems. The data will describe the refinement of motor control in each subsystem as well as the coordination between subsystems. Variables to be investigated include muscle action potentials, lip and jaw movements, and aerodynamics. Both the acoustic and physiologic studies will provide normative information which should be useful in the clinical assessment of communicative disorders. In addition, the data should contribute to a better understanding of the process of speech development, especially as it relates to the motor control of the speech apparatus.